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Choose Mixed signal processsor

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kanni1303

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Hi,
I want to design a controller which capable for capturing the analog signal (from a piezo) and want to process the signal and audio out with assigned sound. Its like music instrument.
I tried with pic16f877a to make the comparison, but not able to finish with the audio out part. with help of ADC I did, and also there was problem if it comes fast to operate, as pic works on 20MHz max, also ADC is slow.
pls guide me a best MSP, for me to make this one. Thanx in Advance.
My requirements are:
ADC,
Comparators
Audio Out with Codec to play WAV or MP3
Storage interface,
USB
and Linux RTOS(preferred)
 

doraemon

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Hello!

Some preliminary ideas.
- You say that 20 MHz is slow. Basically what are your requirements for audio ? What is the sampling rate?
What is the resolution? How many channels?
- Why do you want to use Linux? I mean: if it's a very predictable device (capturing some data, generate some
audio), you don't even need an OS.
- Capturing from a piezo device hints to some kind of keyboard which is sensitive to the pressure / speed of action,
right? Basically you want to sample many keys and play a sound for each one, right?

Dora.
 

kanni1303

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First of all thanx for your reply.
I mentioned it as slow, because of ADC conversion and I need to poll 8 keys which makes sower when I move to 16. As the project involves with musical this speed is necessary.

10Bit resolution, but I need higher as it is ranging between 0 to 1024, I have to get three different bandwidth and this is small, where I m missing several strikes on piezo

It makes me to write simple code :) so I choosed MSP with RTOS.

Yes your wright its very sensitive, even it needs to sens gentle touch, by using amplifiers I was able to meet the sensitivity but with small resolution I m missing lot of strikes as I mentioned in first point

Yes I want to sample 8 keys and in future I want to double it to 16 and for each crystal there will three sounds produced for change in pressure applied.

so with all these I need to select a proper MSP for this project. with my experiment I could make a working kit but controller part isn't efficient to make use of it. kindly suggest me a good MSP.
 

doraemon

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Hello!

Just one thing: why are you polling keys? Usually, polling is not a good method. The best way
to process keys is to use interrupts. It will greatly unload your processor and your system will be
more responsive because you will take action as soon as a key is pressed.

Now as for the processor, you still need to define your system better. What I understand is that
you will receive key event and generate some audio. What is the quality of this audio? Is it
192 ksample / second x 4 channels or is it 8 k sample / second, single channel? What kind of
instrument is it? If it's for example a piano, you will have to process audio samples for each note,
and you have 88 of them for a regular piano. Well, with 16 keys, I guess it's not.... But what this
means is that if you have to output presampled audio with a good quality, you will have to move
samples quickly and continuously to a DAC, therefore you will need some processing power.
If it's just a gadget, you can use any low cost µP.

Dora.
 

kanni1303

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I mention here the keys are inputs, the keys are piezo crystals and connected to ADC. Not as like you though the switch key. The Piezo crystal is disturbed with hand, to play the sound.
The sounds are already prerecoreded wav 1second wav files, depending on which crystal is hit and the magnitude of the pressure, the wav file need to play. we could already made the same with two parts,
Sound Controller - Cubietruck A20 board
ADC Controller with analog multiple channel switch - PIC16f877a
Amplifier.
Now we want to integrate both the ADC and sound controller into one , as the sound generated by this module was not hearable. And in cubie board ADC is 6 bit resolution. hence we need both Digital and Analog signal processor to make this.
And also we are moving to high end processor because we planned to make the same kit to work for Ghatam, Drum, and others with selectable options.
 

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